Field of the Invention
The present invention relates to a switch.
Description of the Related Art
Japanese Patent Laid-Open Publication No. 2011-38568 discloses an inhibitor switch that is mounted on a vehicular automatic transmission to detect a selection range of a shift lever.
FIG. 4 is an exploded perspective view explaining the configuration of an inhibiter switch 10 according to the conventional example that is represented by the inhibiter switch disclosed in Japanese Patent Laid-Open Publication No. 2011-38568. It should be noted that the periphery of a shaft portion 51 in a movable board 5 is illustrated by a cross section.
The movable board 5 provided with movable contact points 7 is provided inside a body case 4 of the inhibiter switch 10 to be rotatable around an axis line X therein, and the movable board 5 includes the cylindrical shaft portion 51 and a contact point holding portion 52 extending in a radial direction (radial direction of the axis line X) from the shaft portion 51.
The shaft portion 51 has an insert hole 55 in which a rotary shaft 91 of a manual shaft 9 is inserted, and joint portions 56 to the metallic rotary shaft 91 are formed in the insert hole 55 to project out of an inner periphery 55a of the insert hole 55 (refer to FIG. 5A).
In the insert hole 55, the rotary shaft 91 is jointed to the movable board 5 in the insert hole 55 by press-fitting a width portion of across flat 92 composed of a pair of planar portions 93 in the joint portions 56, and in this state, the manual shaft 9 and the movable board 5 are jointed to be incapable of rotating relative to each other.
FIGS. 5A, 5B and 5C are diagrams explaining the joint between the shaft portion 51 of the movable board 5 and the width portion of across flat 92 by press fit, wherein FIG. 5A is a cross section made by cutting the shaft portion 51-side of the movable board 5 with a plane A in FIG. 4 and a diagram explaining a general configuration of the joint portions 56 formed in the shaft portion 51 of the movable board 5, FIG. 5B is an enlarged diagram of an essential part in FIG. 5A, and FIG. 5C is a diagram explaining the configuration of the joint portions 56 formed in the shaft portion 51 of the movable board 5 disclosed in Japanese Patent Laid-Open Publication No. 2011-38568.
As shown in FIG. 5A, the joint portions 56 are formed in the insert hole 55 of the shaft portion 51 to project inward from the inner periphery 55a of the insert hole 55, and are provided to be symmetrical across a diameter line Lm of the insert hole 55.
Each of the joint portion 56 has both side portions across a straight portion 561 positioned in the center in the longitudinal direction (right-left direction in the figure) and both the side portions project closer to the diameter line Lm than the straight portion 561. The portions projecting closer to the diameter line Lm form press-fit portions 57A in which the width portion of across flat 92 of the manual shaft 9 is press-fitted.
Each of tip surfaces 571 of the press-fit portions 57A is formed as a planar surface in parallel to the diameter line Lm, and a press-fit amount Wa of the width portion of across flat 92 to each of the press-fit portions 57A is equal over the entire length of the press-fit portion 57A in the longitudinal direction (direction of the diameter line Lm).
A diameter D1 of the rotary shaft 91 of the manual shaft 9 is slightly smaller than a diameter D2 of the insert hole 55 in the shaft portion 51, and each of the press-fit portions 57A of the movable board 5 has a section in which the width portion of across flat 92 of the manual shaft 9 is not press-fitted (section between an intersection point Px between the press-fit portion 57A and the width portion of across flat 92, and a connecting portion 571a between the press-fit portion 57A and the inner periphery 55a of the insert hole 55: refer to an area A in FIG. 5B).
Here, when the width portion of across flat 92 of the manual shaft 9 is press-fitted between the press-fit portions 57A, stress in a direction of separating the press-fit portions 57A from each other (direction of widening the insert hole 55) acts on the press-fit portions 57A (refer to an arrow B in the figure).
This stress concentrates on the connecting portion 571b between each of the press-fit portions 57A and the inner periphery 55a of the insert hole 55, which possibly causes cracks CK on a basis of the connecting portion 571b to be generated or the shaft portion 51 to be broken.
In the inhibiter switch according to Japanese Patent Laid-Open Publication No. 2011-38568, as shown in FIG. 5C an arc-shaped notch portion 58 is formed in the connecting portion between a press-fit portion 57B and the inner periphery 55a of the insert hole 55, which alleviates stress concentration due to the press fit to prevent fracture of the shaft portion 51 or generation of the crack on the shaft portion 51.
Here, when rotation of the movable board 5 around the axis line X is repeated by the manual shaft 9, the support of the manual shaft 9 (rotary shaft 91) in the movable board 5 is gradually weaken due to aging of the press-fit portions 57B of the movable board 5.
In a case of the inhibiter switch in Japanese Patent Laid-Open Publication No. 2011-38568, a length La of the press-fit portion 57B in a direction of a diameter line Lm is shorter than a length Lb of the conventional press-fit portion 57A as shown in FIG. 5B, and a length (press-fit length) of the press-fit portion 57B involved in the support is made small.
Therefore, when the support of the rotary shaft 91 (metallic shaft member) in the manual shaft 9 becomes weak due to the aging of the plastic press-fit portions 57B, the looseness of the movable board 5 to the manual shaft 9 becomes larger than in the conventional inhibiter switch.
Therefore, there is a need of preventing the fracture of the movable board at the time of press-fitting a metallic shaft member, and at the same time, as well as suppressing generation of the time-dependent looseness of the movable board.